The bone marrow is the principal source of the many different types of cells that circulate in your blood stream. The term myelodysplasia describes certain abnormalities in the production of these blood cells. Myelodysplastic syndrome (MDS) refers to at least 5 different entities, all of which interfere with the growth of blood cells in the bone marrow. The differences among them are found in the appearance of the cells under the microscope and are helpful primarily in determining prognosis.

MDS frequently progresses to a form of acute leukemia. Leukemia is a cancer of the blood cells. But in the case of leukemia, there is an overproduction of immature cells (blasts) circulating in the blood and an underproduction of healthy cells. In MDS, there is usually, but not always, only an underproduction of healthy cells. The progression to acute leukemia is so common that MDS used to be known as preleukemia.

Stem Cells

The bone marrow contains stem cells, which have the capacity to become any of the cell types that circulate in the blood stream. These stem cells normally undergo a maturation process that results in mature cells with fixed functions:

Once cells have matured in the bone marrow, they are released into the blood circulation. MDS interrupts the normal maturation process of blood cells.

Causes and Complications

The exact cause of MDS is unclear, but certain factors are believed to increase risk. These include radiation for the treatment of cancer, certain drugs and chemicals, genetic factors, and some birth defects.

Infection—If immune cells (white blood cells) are depleted, even small infections can be serious.

Anemia—When the number of red blood cells decreases, anemia may develop. A lack of red blood cells reduces the oxygen-carrying capacity of the blood and may cause fatigue, shortness of breath, and palpitations.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.